1 Department of Critical Care, Respiratory Institute, Cleveland Clinic Foundation, Cleveland, OH, USA.
2 Centre for Human and Applied Physiological Sciences, School of Basic and Medical Biosciences, King's College London, London, UK. Luigi.camporota@kcl.ac.uk.
3 Department of Adult Critical Care, Guy's & St Thomas' NHS Foundation Trust, East Wing 1 offices - St Thomas' Hospital, Westminster Bridge, London, SE1 7EH, UK. Luigi.camporota@kcl.ac.uk.